The Example

I noticed every now and then that the "Service Engine Soon" light would come on, then shut itself off after a brief period (a minute or so). However today, I was stopped at a light and it came on. It shut off after about 5 minutes, but once I reached my destination shortly thereafter, it came on again and stayed on.

I floored it to see if that would clear it up, but the car runs like a honda, I'd put the 0-60 at 10 seconds. I dont have any idea what it could be, besides maybe a fuel filter? Only things I have done to the car is a new Delco air filter, so that couldn't be it. I haven't had it serviced yet either. 51'000 miles on it, just got it last week. Can anyone help me before I take it to :gasp: a mechanic?

vettenuts

Well, the fuel filter per se won't set a code. You need to pull the error code that is setting the light. Look under the dash for the ALDL plug, it's on the driver's side. Remove the plastic cover. Get a paper clip and then bend into a "U". You want to connect pins "A" and "B", which are on the top row and are the two pin closest to the center of the car. If you are old like me, you won't be able to read the letters Anyhow, with the key off, insert a your bent paper clip into these two holes. Now, turn the key to run but don't start the car. Your SES light should flash code 12 (flash pause flash flash). It will do this three times. This tells you the diagnostic circuit is functioning. Next, it will flash any error codes, each one three times prior to moving to the next one. Once all the error codes have been displayed, code 12 will flash again to tell you the end of error codes has been reached. If you leave the key on, the sequence will repeat itself. Post your codes, someone will decode them for you.

PS: Mechanic is a last resort, unless of course you live near David F, then I wouldn't waste my time and would instead take it to him

The Example

Well, I looked underneath the dash on the drivers side, and I couldn't find anything. Can you explain where exactly the ALDL plug is?

W4ZG

On my 89 coupe, it is a black female connector approx 1/2" tall and 2" wide with 12 openings... seen with cover removed...it is mounted about 6" to the right of the steering column on the carpeted panel that covers the lower access to the dash..should be very visable without tearing into the lower dash itself... ...unless someone got there before you and tucked it up out of sight!

The Example

Yes, when I had the pedal at normal speeds, it was fine, but after I pushed it down maybe halfway the car did exactly what you said. Took FOREVER to get up to 50.

The Example

Oh yeah, I forgot. I just looked again for the ALDL and saw no signs of it where W4ZG said it would be. I pulled the three screws keeping the lower dash on, and theres a ton of crazy connectors in there that I don't want to mess around with until I know which is which. The closest one had a yellow wire coming out of it, and if IIRC thats for the airbags, so thats no good. Also saw some electrical tape

88L98

ill take a picture of it for you to help you out... brb

88L98

ok my car is locked up in the car port and im in my boxers so i didnt go out to my car, but this is what it looks like, this is in an iroc-z. it looks the same in the vette, it just doesnt have the plastic surrounding and the foam underneath it. its the black looking grid

The Example

Aha, found it! It wasn't in the place where the pic shows, it was waaaay back in the dash. Someone else has been here Oh well, I wouldn't have known what I was looking for without that pic, I am in your debt 88L98!

PS - I am also in my boxers and it hasn't stopped me yet!

The Example

Wait a minute......I think I know how this whole SES business started.

Dad - "Sure son, you can drive without an air filter for a little while"

::15 miles later::

Me - "Wait a minute, thats the worst advice I've ever heard!"

::After getting new filter and installing it::

Me - "I sure hope nothing bad happens"

Later that day.....

The Example

Well, I put a paper clip into slots A and B after some difficulty in keeping it from falling out, maybe it was too big? And then I turned the ignition to the setting right before it starts turning over, and nothing happened. All of the lights came on and disappeared except the SES light which remained on and did not blink. I don't think I had the paper clips in the right position. There seems to be a brass piece in the middle, with a small hole below it and a bigger one above it. Which one do I need to make a connection?

88L98

the top row goes like this:

FEDCBA

each letter represents a port the top row. put the paper clip between B and A.

if you drove without an air filter that was not smart at all. a piece of grass or something destroyed the wire in your Mass Aif Flow sensor. never ever ever ever ever drive without an air filter unless you are running at the track. that was not a good idea at all. your looking at about 150-175 bucks now

The Example

I don't think that is what happened. If my MAF was gone, I think I'd notice it, but then again....

Anyways, I pulled a code 43, which is knock sensor IIRC. Happens intermittently, on and off type thing. How would I go about resolving this?

88L98

is this on the 87 or 91

The Example

The 1991, the 87 has performed flawlessly since we got it a few months ago, save a dead battery and a can of Pepsi spilled onto the drivers seat motor

88L98

oops my bad. the 91 dont even have a MAF sensor. sorry for the misinformation. about the knock sensor, check the connector on the knock sensor and make sure it is getting good connection and test it with a multimeter to see if its getting current.

The Example

Where might I find the knock sensor? I'm going to take another look first thing in the morning, (bad garage lighting).

Ruby_Roadster

It's the Knock Sensors - replaced mine and (touch wood) haven't had a problem since. When either one or both go bad, replace both - because if one goes it very likely that the other one will fail soon after.

Situated underneath, change only when collant is cold, don't overtighten (use a torsion wrench)

vettenuts

91 only has one knock sensor, it is on the passenger side. There are number of circuit checks that should be done, the simple ones are a resistance check of the knock sensor to ground (block). Should read 3300 and 4500 ohms. If the knock sensor checks out, then the voltage needs to be checked. With engine up to temp, key on, engine off, disconnect wire and use a digital voltmeter between the wire that connects to the knock sensor and ground. Should be 4 to 6 volts. From here, you move on to the mem-cal in the ECM. Hopefully it won't come to that.

PS: There is also a system check run by the ECM, it may fail this check if you are running very high octane fuel and set code 43.




[Modified by vettenuts, 8:57 PM 8/2/2001]